Sentinel Node Biopsy

J. Taylor Whaley, MD
Last Modified: December 29, 2014

What is a sentinel node biopsy?

  • A sentinel node biopsy, or sentinel lymph node dissection, is a procedure that is performed to look for cancer in the nearby draining lymph nodes after a cancer is diagnosed. When a cancer is discovered, it is very important for your medical team to know how aggressive the tumor is and if the tumor has spread beyond its original location. The first place most cancers spread to is the surrounding lymph nodes. The purpose of the procedure is to obtain a tissue sample of the nearest lymph nodes to help with the staging of the cancer.
  • There are thousands of lymph nodes found throughout the body, which serve a very important role in the immune system of filtering circulating fluids, as well as housing white blood cells that help fight infections. When tumor or cancer cells spread to lymph nodes, the initial site of spread is referred to as the sentinel lymph node. When lymph nodes are involved with cancer, they are frequently enlarged, painless, and hard.
  • Sentinel lymph nodes biopsies are most frequently performed in breast cancer, melanoma, and other skin cancers. Its role in other types of cancers are being investigated. Sentinel node biopsies have been used for the past 10-20 years, most frequently in breast cancer. They have replaced the axillary dissection procedure, which removed most of the nodes in the underarm; however, if the sentinel node is involved with cancer, a full dissection will frequently be performed.
  • Sentinel node biopsies are outpatient surgeries, and are well tolerated with few complications.

How is this test performed?

  • A sentinel node biopsy is performed by a surgeon to evaluate the extent of spread of a newly diagnosed cancer. Frequently, the sentinel node dissection will be performed with the lumpectomy, mastectomy, or surgical resection of the tumor.
  • To perform a sentinel lymph node biopsy, the surgeon will inject the area near the tumor with a very small amount of a radioactive tracer or a blue dye. The substance injected is based on the surgeon’s preference. If radiotracer is used, the amount of radiation is very low, even less than that of an X-ray. The substance is injected just below the skin near the tumor location (or where it was removed from). For breast cancer, it can also be injected near the areola. The injection is done anywhere from 30 minutes to several hours before the dissection. Because all fluid that surrounds the area is drained to lymph nodes, the sentinel node will take up the dye or tracer.
  • The surgeon will make a small incision after numbing the area. Using a Geiger counter, which is a small device that is very sensitive to low doses of radiation, the surgeon can locate the lymph node or nodes that drain the area near the tumor. If the blue dye is used, the lymph node will appear blue. The surgeon will then carefully remove the lymph node or nodes.
  • After the tissue is collected, the sample is sent to a pathologist for evaluation. A pathologist is a type of doctor that specializes in looking at tissues under the microscope. After the pathologist has established a diagnosis, a report will be generated for your doctor.
  • A sentinel lymph node dissection generally takes 45-60 minutes to perform.  If a tumor resection will happen at the same time, the procedure will be longer.

How do I prepare for a sentinel lymph node biopsy?

  • There is minimal preparation for a sentinel lymph node biopsy.
  • If general anesthesia will be used, you will need to fast prior to the procedure. If local anesthesia will be used, no preparation is needed; however, if you are on blood thinners, your doctor will likely have you stop them several days in advance. You should also stop taking aspirin, some anti-inflammatory medications, and any supplements that may increase the risk of bleeding. These details should be discussed when the biopsy is scheduled.

What is recovery like?

Your surgeon will discuss specific recovery issues with you. In general, you will be up and moving the day after surgery, with some limitations to your normal schedule and exercise routine in the first week or so. After surgery, you could experience any of the following side effects:

  • Blue urine and greenish colored stool for 24-48 hours after the injection of blue dye as it is excreted from your body. You are NOT radioactive after receiving the radioactive tracer.
  • Pain, numbness and/or sensitivity in the area where the lymph nodes were taken.
  • A seroma could develop. A seroma is when lymph fluid collects, instead of draining its normal route through the lymph nodes. It is not worrisome, but can be uncomfortable. Most go away naturally, over time, but occasionally need to be drained in the office with a needle (an easy, painless procedure).
  • Lymphedema is a chronic swelling in the arm or leg, on the side of surgery. There is a low risk of developing lymphedema after this procedure, though this risk is life-long. Talk to your care team about lymphedema risk and what you can do to minimize your risk of developing lymphedema.

How do I get the results of the test?

  • Following the biopsy, the tissue sample is processed by a pathologist. A preliminary report may be given to the doctor using a frozen sample of the tissue; however, the final report generally takes several days.
  • The details of the diagnosis are found on the final pathology report. Because reports are generated for other medical professionals, the terminology is often medically oriented and can be difficult to interpret. Talk with your healthcare team about your results.
  • Ask for a copy of the report to keep in your personal files.


From the National Cancer Institute